Create a SD card with the demo

You need a 1 GB SD card (or more) and to download the image of the demo. The image is compressed to reduce the amount of data to download.
This image contains:

a FAT32 partition with the AT91Bootstrap, U-Boot and the Linux Kernel (zImage and dtb).

an EXT4 partition for the rootfs.

Multi-platform procedure

To write the compressed image on the SD card, you will have to download and install Etcher. This tool, which is an Open Source software, is useful since it allows to get a compressed image as input. More information and extra help available on the Etcher website.

Insert your SD card and launch Etcher:

Select the demo image. They are marked as "SD Card image" in the demo table above. Note that you can select a compressed image (like the demos available here). The tool is able to uncompress files on the fly

Select the device corresponding to your SD card (Etcher proposes you the devices that are removable to avoid erasing your system disk)

Click on the Flash! button

On Linux, Etcher finally asks you to enter your root password because it needs access to the hardware (your SD card reader or USB to SD card converter)

then the flashing process begins followed by a verification phase (optional)

Once writing done, Etcher asks you if you want to burn another demo image:

Your SD card is ready!

Alternative Linux procedure (Use at your own risk!)

Uncompress the image:

bunzip2 linux4sam-poky-sama5d2_xplained-5.0.img.bz2

The compressed image will be removed and you will get the uncompressed image named linux4sam-poky-sama5d2_xplained-5.0.img.

Insert your SD card. To identify the device, use the dmesg command.

If you have an integrated SD card reader, you should have something like this: